Regulation of gene transcription by estrogen and progesterone. Lack of hormonal effects on transcription by Escherichia coli RNA polymerase.

Abstract

Estrogen and progesterone markedly stimulate transcription of ovalbumin and conalbumin (transferrin) genes in chick oviduct as measured by hybridization of labeled RNA synthesized in isolated nuclei to immobilized plasmid DNA containing these gene sequences. Using this direct assay for specific gene transcription, we explored the basis of previous reports indicating that steroid hormones also cause changes in oviduct chromatin structure that can be detected by Escherichia coli RNA polymerase. We observed no effect of these hormones on the ability of E. coli RNA polymerase to transcribe specifically the conalbumin and ovalbumin genes 8 1/2 h after hormone administration when transcription of these genes by endogenous RNA polymerase was elevated 5- and 30-fold, respectively. Furthermore, we were unable to detect any significant effect of either of these hormones on the total number of E. coli RNA polymerase binding sites in oviduct nuclei or chromatin. In contrast, after several days of hormone administration, we detected an apparent preferential ovalbumin RNA synthesis by E. coli RNA polymerase and this effect could be transferred to unstimulated nuclei by a 0.35 M salt extract of active nuclei. However, further experiments revealed that this preferential ovalbumin RNA synthesis is an artifact produced by transcription from contaminating ovalbumin mRNA. We conclude that E. coli RNA polymerase does not recognize steroid hormone-induced changes in oviduct chromatin.